<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>46页代码</title>
</head>
<body>
<script>
    var f=true;//false报错，
    var res=f||s;
    alert(res);//true时弹出true
   // alert(s||f);//这样还是会报错
    var ar=[1,2,3,4];
    ar.a="add";
    for(var v in ar){
        console.log(v);//而且这个打印出来好像是字符串，
    }
    for(var m of ar){
        console.log(m);
    }

</script>
</body>
</html>